An item that judges a motion state (walking, running, going up or down stairs) from accelerations in the vertical and advancing directions outputted from a triaxial acceleration sensor is known as a pedometer that judges whether or not the motion state of a user is running.
Additionally, an information processor apparatus is known that calculates a walking/running judgment frequency and a walking/running judgment variance from sensor data made by sensing a user's motions. The information processor apparatus then judges whether the user is walking or running according to the product of the walking/running judgment frequency and the walking/running judgment variance.
Japanese Laid-open Patent Publication No. 2008-262522 and Japanese Laid-open Patent Publication No. 2010-198595 are examples of related art.
As described above, judging the magnitude of a vertical acceleration is used when judging whether or not the user is in a running state based on the acceleration in the vertical direction. If the relation between the axis detected by the acceleration sensor and the vertical direction is not fixed, the vertical acceleration is computed from a sensor detection value according to the sensor orientation. In this case, the large amount of computing to conduct repetitive operations to derive the vertical acceleration is limited to hardware that includes a judgment function.